1044 



SUBMAMMALIAN VERTEBRATES 



Few species of turtle show external sexual 

 dimorphism. An exception is Teirapene Car- 

 olina, in which the eye of the male is red 

 whereas that of the female is brown (Blake, 

 1921). 



The male tuatara, Sphenodon punctatum, 

 the sole living representative of the order 

 Rhynchocephalia, is much larger than the 

 female and has a conspicuous dorsal crest 

 with white spines. In the breeding season 

 the male's crest may become erect and 

 swollen (Thomas, 1890). Remarkably little 

 is known about the reproductive system and 

 its function in this fascinating reptile. 



The gular skin fold which the lizard Anolis 

 can erect from its throat is a striking mas- 

 culine characteristic. Male lizards of some 

 species distinguish themselves by dorsal 

 crests and bright colors. 



Among the snakes, certain scales or scaly 

 tubercles near the anus may show sexual di- 

 morphism, and, as in the lizards, the slight 

 bulging of the penial sacs on external ex- 

 amination distinguishes the male from the 

 female (Blanchard, 1931; Noble, 1934; Le- 

 derer, 1942). The tip of the tail of the male 

 fer-de-lance, Bothrops atrox, may be a 

 bright yellow. There is reason to think that 

 this wriggling, twisting tail-tip may lure 

 lizards, toads, and other food within striking 

 distance (Burger and Smith, 1950) . The male 

 Paraguayan anaconda is smaller than the 

 female, and his pelvic spurs are better devel- 

 oped (Lederer, 1942) . Males of Engyrus car- 

 inatus, a New Guinea bold snake, have 

 pelvic spurs, whereas these structures are 

 missing in most adult and all juvenile fe- 

 males (Stickel and Stickel, 1946). Male boas 

 and pythons use their spurs to scratch the 

 body of the female during mating (Davis, 

 1936). Tubercles on the chins of some colu- 

 brid snakes are tactile organs; if the tuber- 

 cles are covered with tape, the male will not 

 court the female (Noble, 1934). Davis 

 (1936) has reviewed the role of spurs, tu- 

 bercles, etc., in the courting beliavior of 

 snakes. 



Although evidence will l)e presented later 

 for endocrine control of the adult develop- 

 ment of some accessory sex structures, it 

 must be remembered that genetic factors 

 also ])lay tlieir role. Relative degrees of con- 



trol exercised by genes and hormones con- 

 stitute a significant area for research. 



VIII. Eflfects of Orchiectomy 



Fish 



Ablation of gonads helps to disclose the 

 structures, physiologic processes, and be- 

 havior which are partly or completely under 

 the control of testicular or ovarian hormones 

 ( see Pickford and Atz, 1957, for review ) . The 

 most frequently observed result of the cas- 

 tration of male fish has been a loss of the 

 special, occasionally brilliant, skin color in 

 those species with color dimorphism. Some- 

 times there is a seasonal pigmentary change 

 in the chromatophores, or pigment-bearing 

 cells. Such change is associated with the time 

 of spawning, and is referred to as Hoch- 

 zeitskleid, or nuptial coloration. If castra- 

 tion is performed before the breeding season, 

 the nuptial coloration fails to appear; if 

 during the season, the color may rapidly 

 fade. Removal of only one testis has little or 

 no effect; apparently the remaining gonad 

 can release enough androgen to maintain 

 normal coloration. Loss of male coloration 

 due to castration has been demonstrat(>d in 

 several genera. ^'^ 



The male Japanese bitterling also has 

 pearl organs, 5 to 10 small dermal excres- 

 cences like white warts on the anterior part 

 of the head. Orchiectomy interferes with 

 their development ( Tozawa, 1929) , as it does 

 with the growth of the gonoj^odium in Gam- 

 busia (St. Amant, 1941; Turner, 1941a). 



Amphibia)is 



Orchiectomy has shown that many male 

 secondary sex characters are under the con- 

 trol of testicular hormones. Steinach (1894) 

 found removal of the Samenbldschen, a sac- 

 like appendage of the mesonephric duct, 

 from a frog had no effect on the sex charac- 

 ters, but castration before the breeding sea- 

 son resulted in the failure of amplexus to 

 occur. Among the urodeles, orchiectomy in 

 Discoglossiis is followed by prompt regres- 



'•'Thc stickleback, Gasterosteus (Bock, 1928; 

 Becker and Lehmensick, 1933; Ikeda, 1933), tlie 

 bitterling, Acheilognathus (Tozawa, 1929), and 

 Phuxinus (Kopec, 1927), Halichoeres (Kinoshita, 

 1935), Oryzia.s (Niwa, 1955), and Amia (Zahl and 

 Davis, 1932). „ 



